Conductor and filaments therefor containing organic derivative of cellulose



Aug. 16, 1938. W. WHITEHEAD 2,126,359

CONDUCTOR AND FILAMENTS THEREFOR CONTAINING ORGANIC DERIVATIVE OFCELLULOSE Filed July as, 1934 FILAMENTS CONTAINING ORGANlC DERNATIVE OFCELLULOSE AND TRICRESYL PHOSPHATE METALLIC WIRE INVENTOR -iHlom WHI+hOdfiame-proofed artificial material, such as fila-. ments, yarns andfabric, the base material oi" Patented Aug, 16, 1938 PATENT OFFICECONDUCTOR AND I'ILAMENTS THEREFOR CONTAINING ORGANIC DERIVATIVE OFOELLULOSE William Whitehead, Cumberland, Md., assignor to CelaneaeCorporation at America, a corporation of Delaware Application July 28,1934, Serial No. 737,045

4 Claims.

This invention relates to the manufacture of a which is an organicderivative of cellulose and more particularly to filaments and yarnsespecially adapted for use as an insulating covering for electricconductor wires and the like.

An object of the invention is the economic and expeditious production ofa yarn or filament that is an insulator of electric current, that isfiame-proofed and that readily lends itself for braiding, wrapping andother operations to form a'uniform and tight covering for electricwires. Other objects of the invention will appear from the followingdetailed description.

For electrical insulation, as a covering for wires, etc, there isrequired a yarn or group of filaments that has a lowelectro-conductivity, one that is not tacky, one that is not injuriousto the hands of the operator and also one preferably composed ofsubstantially continuous filaments so that closer, flatter and moreuniform wrappings or braid may be formed. A further property desirablein a .wire covering is low infiammability so that the covering will notsupport combustion but will cease burning upon removal of applied heat.

I have found that a specially prepared filament or yarn of an organicderivative of cellulose, which has the inherent property of being anonconductor, may be made to have all the other desired properties alongwith such properties as good strength and pllability for passing throughguides, etc. of a device for braiding or wrapping wires, etc. I havefound that a yarn or filament containing a large percent of a phosphoricacid ester is fiame-proofed and otherwise suitable for electricalpurposes.

Yarns and filaments, made according to this invention, containincorporated in the filaments the agentwhich reduces theirinfiammability. Moreover, they are not tacky or gummy and may be woundin packages and rewound without causing difiiculty due to stickingtogether or to ms.-

chine parts. The yarns are not stiff and gummy as a coated yarn, but aresoft and pliable and capable of being flexed into sharp angles, as inbraiding, without breaking or causing uneven braiding. In their passagethrough machines they do not deposit sticky material on the guides,needles. etc.

According to my invention I form filaments, a plurality of which may begrouped together either in untwisted or parallel relationship or intwisted form, of organic derivatives of cellulose,

port combustion unless a fiame is applied thereto.

As soon as the material is removed from the flame, it ceases burning.

This invention is particularly applicable to the production, forelectrical insulation purposes, of

a yarn containing a number of substantially continuous filaments heldtogether by a twist preferably less than 5 turns per inch, which amountof twist is often desired in forming fiat insulating coverings forwires. This invention is also applicable to the productions of threads,assemblies or bundles of a number of. continuous filaments which may bein parallel relationship or which may be twisted together with anydegree of twist, as well as artificial bristles, straws. short lengthsof staple fibers, or yarn spun from such staple fibers.

The yarns, filaments, etc. are preferably formed of cellulose acetate.However, other organic derivatives of cellulose, such as the otherorganic esters of cellulose and cellulose ethers, maybe employed.Examples of the other organic esters of cellulose are cellulose formats,cellulose propionate and cellulose butyrate, while examples of celluloseethers are niethyl cellulose, ethyl cellulose and benzyl cellulose.

The filaments, etc., may be formed in the usual manner of spinningfilaments by either the wet or, more preferably, by the dry method ofspinning. Thus, a spinning solution containing one part celluloseacetate and 3 parts solvent, such as acetone, may be formed. To thisthere may be added the flame proofing agent and the solution filteredand extruded through suitable orifices into an evaporative atmospherefor the solvent.

As the flame-proofing agent there may be employed a large amount,preferably from 20 to 60 per cent on the weight of the organicderivative of cellulose, of an alkyl, aryl or mixed alkyl-aryl ester ofphosphoric acid or a mixture of such esters. The aryl ester ofphosphoric acid may be a mono-, dior tri-hydroxyl derivative of thebenzene series. For example, the esters may be mono-, dior tri-cresylphosphate, mono-, dior tri-phenyl phosphate, mono-, dior trl-xylenylphosphate and the phosphates of the hydroxy derivatives of the higherhomologues of the benzene series. The ester may be formed of one ofthese hydroxy-benzene groups or each ester may contain a mixture of twoor three different bydroxy-benaene groups such as would be produced bythe reaction of phosphoric acid and such hydroxy-benaenes as are roundin coal tar acids, commercially sold under the name of cresylic acid.The esters may be homogeneous hydroxybenzene phosphoric acid esters orthey may be mixed hydroxy-benzene esters of phosphoric acid.

In connection with or as a substitute tor the hydroxy-benzene phosphoricacid esters, there may be employed the alkyl esters of phosphoric acid,for example, trimethyl phosphate, triethyl phosphate and tributylphosphate. Further,

and not as a limitation, the following examples are given:

Example I 100 parts by weight of cellulose acetate is dissolved in 300parts of a volatile solvent such as acetone. To this solution isadded'20 parts of tricresyl phosphate or other ester of phosphoric acid.Alter filtering, the mixture is extruded through suitable orifices intoan evaporative atmosphere to form filaments of 1.5 to 3. denier. Thefilaments are grouped in suillcient number to form the yarn of desiredsize and given from 1 to 5 turns per inch and wound into packages.

Example 11 100 parts by weight of cellulose acetate is dissolved in 300parts of a volatile solvent such as acetone. To this solution is added50 parts of tricresyl phosphate and the same processed as in 7 ExampleI.

Example III The yarn from. either Example I or II is rewoundonto'suitable braider tubes for use with any of the commercial machinesand is wrapped spirally or braided upon a copper wire of any suitabledimension, say inch diameter. During the forming operation of Example Ior II or in rewinding, a lubricant of about 1 to 4 per cent oil, such asolive oil, may be applied to the yarn.

The wire is evenly, uniformly and tightly covered by the yarn, and theassembly is non-tacky and contains no coating material injurious to theskin of those that may handle it. Held vertically in a flame thecovering slowly burns but combustion ceases as soon as the applied flameis removed. The yarn formed in Example I has a conductivity of 30,000 I.R. (Insulation Resistance) kilomegohms per end while the yarn formed inExample II has a conductivity of 12,000 I. R. kilomegohms per end.

Largeamounts oi the organic esters oi phosa,iae,aso

plroric acid may be incorporated in the yarn via the spinning dopewithout destroying the stability oi the spinning dope and withoutrendering the yarn weak or diillcult to handle in textile manipulation.The cross section of the filaments remains the same as those formed fromnormal spinning-solutions, giving the beautiful appearance to theproduct of the organic derivatives 01' cellulose.

The yarns or filaments, etc., may be colored, tinted or dyed prior to orafter application to the wire or other object to be insulated. The wiremay be coated with other insulators either before or after the coveringof organic derivative of cellulose is applied. For example, a coating ofrubber, enamel, etc., may be applied directly to the wire or to the wirecovered with a wrapping of yarns containing organic derivatives 01cellulose.

The yarns and filaments may be used, other than for electric wirecovering, any place that a flame-mooted or slow burning material 01' atextile nature is required. The yarns and filaments may be woven,knitted. or netted, alone or in combination with asbestos yarns, finewire and the like into draperies or curtains for theatrical purposes orother places where it is desired to greatly reduce fire hazards. Theseimproved yarns are pliable and lend themselves to textile operations andare strong, lending strength to draperies, etc. containing them.

In order to further illustrate my invention, reference is had to theaccompanying drawing which represents an electric conductor covered withthe filaments of my invention.

It is to be understood that the foregoing detailed description is merelygiven by way 01 lllustration and many alterations may be made thereinwithout departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patentis:

1. Filaments 01' good electrical insulating properties containing anorganic derivative of cellulose and tricresyl phosphate, in an amountequal to 50% or the weight or the cellulose derivative, as the soleplasticiaer for the cellulose derivative.

2. Filaments of good electrical insulating properties containingcellulose acetate and tricresyl phosphate, in an amount equal to 50% oithe weight of the cellulose acetate, as the sole plasticizer for thecellulose acetate.

3. An electric conductor comprising a metallic wire having a covering offilaments of good electrical insulating properties containing an organicderivative 01' cellulose and trlcresyl phosphate, in an amount equal to50% of the weight of the cellulose derivative, as the sole plasticizer.

4. An electric conductor comprising a metallic wire having a covering offilaments of good electrical insulating properties containing celluloseacetate and tricresyl phosphate, in an amount equal to 50% of the weightof the cellulose acetate, as the sole plasticizer.

I WILLIAM WHITEHEAD.

